The present invention relates to an apparatus for reading and/or recording data on a rotating disc, comprising a transducer for reading and/or recording data on the disc, the transducer being mounted on a carriage which is movable in a radial direction with respect to the disc along a guide mounted on a base and urged against the carriage by a resilient member interposed between the guide and the base, and a drive roller for moving the carriage on the guide.
In a known apparatus, disclosed in U.S. Pat. No. 4,323,939, the carriage is slidable on two parallel cylindrical guides by means of three rollers which are disposed in a triangular configuration; one roller rolls against one of the guides while the other two rollers roll against the other guide. One of the two guides is fixed to the base while the other guide is movable, being mounted on a resilient member which presses the movable guide against the corresponding roller. The carriage is moved by a drive roller having its axis of rotation parallel to the plane passing through the two guides by means of a flexible strip which is wound around the roller and fixed to the carriage. That arrangement is bulky and of substantial weight due to the provision of the three rollers and the two guides.
In another known apparatus, shown in U.S. Pat. No. 3,881,189, the carriage is formed by a cylindrical bar which is slidable between two fixed supports. The cylindrical bar is moved by a drive roller and by a metal strip which is wound around the roller and which is fixed at its ends to two spaced collars which are fixed to the bar.
The roller rolls on a resilient metal plate which is fixed at its one end to one of the two collars, parallel to the axis of the bar, to apply a resilient force to the bar for the purpose of taking up clearances caused by wear of the bar relative to the supports.
A further resilient strip is connected between the bar and the supports to prevent the bar from rotating about its axis. Since the bar is slidable on the fixed supports, that arrangement may involve abnormal conditions of sliding movement due to unpredictable variations in the level of stiction, with resulting inaccuracies in the micro-metric movements of the bar.